Thermostat



(No Model.)

B. H.'DAVIS & R: WESTERVELT. THERMOSTAT.

No; 400,312. Patented Mar. 26, 1889.

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UNITED STATES PATENT OFFICE.

ETNA HYDE DAVIS AND REUBEN \VESTERVELT, OE ELMIRA, NEV YORK.

TH ERMOSTAT.

SPECIFICATION forming part of Letters Patent No. 400,312, dated March 26, 1889;

Application filed September 4, 1888. Serial No. 284,570%: (No model.)

To aZZ whom it may concern:

Be it known that we, ETNA HYDE DAVIS and REUBEN WEsTERvELT, citizens of the United States, residing, at Elmira, in the county of Chemung and State of New York, have invented certain new and useful Improvements in Electrical Thermostats; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

Our invention is concerned with improvements in electrical thermostats which are employed to operate one or more electrical circuits for various purposes.

The object of our invention is to render the action of such thermostats more certain than has hitherto been possible. The difficulty with such thermostats has been that the contacts made by the thermostat on an increase or decrease of temperature have been necessarily weak and fluctuating. In the nature of the case the initial contact made by a gradual increase or decrease of the temperature is excessivelyfeeble. More over, it is noticeable in practice that the contacts at first are vibrating contacts, which fact also interferes greatly with the perfect operation of the apparatus, and the result has been that the motors in circuits controlled by the thermostat have been imperfectly operated, or with extreme slowness. lVe obviate these defects by employing in connection with each thermostat a pair of magnets, one of which is connected with each point of contact of the thermostat in such a way that when the initial contact is made one of the magnets will be energized and will close a short circuit around the thermostatpoint. By these means the motors controlled by the thermostats are operated positively and firmly, the result being that the apparatus works with much greater efficiency than heretofore.

NVe have illustrated our invention in the accompanying drawing, which represents a front elevation of a thermostat having our invention applied to it, showing also a diagram of the circuits.

Referring to the drawing, A is our thermostat, and B is the expansible element thereof, the said expansible element being a compound bar made up of steel and hard rubber supported at one end in a post, C. The post C and the base upon which it is supported are both metallic and are in electrical connection with the steel portion of the compound bar. 011 the opposite sides of the free end of the thermostatic bar are insulated posts D and E, each one of which forms part of a branch circuit extending from a battery, XV, through the thermostatic bar.

011 a separate base, F, is supported a pair of magnets, G and H, having a common armature, I. The latter is in electrical connection with the base of the thermostat, and, moreover, is centrally pivoted and adapted to swing upon its pivot when operated upon alternately by the two magnets. Attached to the armature is a metallic arm, J, which swings back and forth into and out of contact with the springs K and L, the latter being connected, respectively, to insulated posts N and O. The two positions are shown in the full and dotted lines in the drawing.

e have shown the magnets supported upon a separate base to indicate that they are not necessarily 011 the same base with the thermostat at all. They may, however,be attached to the thermostat-base, if preferred; but so far as the operation of the parts is concerned the magnets and the parts actuated thereby might as well be located at a distance, and in many instances they will be so located.

In the drawing we show at the right motor M, adapted to actuate a valve for purposes of heat regulation. This is a more detail, and our invention may be applied to the thermostat without introducing the heat regulation at all, the thermostat being adapted for use with any system of circuits devoted to any desired purposes.

The operation of the apparatus is as follows: The circuit from battery XV enters at post G and travels by bar B to one or the other of the posts D and E. From post D the circuit travels through magnet G and the insulated post N, from which it passes to the motor, as shown, and from there back to the battery, when the proper connection is made. The circuit from contact E passes similarly through the magnet H, insulated post 0, and motor. Suppose, now, that the variation of the temperature causes the bar to make con tact at post E. The initial contact will be sufficiently strong to cause some current to pass. This will immediately energize the magnet H and throw the armature and its connected arm into the position shown in the dotted lines in the drawing. This being the case, the circuit, instead of passing along the bar to the post,will now pass through the base of the thermostat and the armature-post to the armature, thence through the arm J, and to the springs L. From there it goes to the motor, thus cutting out contact at the point of the thermostatic bar; It is thus evident that there may be as much weakness or fluctuation as you please at the point of the bar, yet it will not affect the contacts which now control the motor. In this way the motor will get the full strength of the current, and will be actuated accordingly.

We make the contacts with which the arm J co-operates in the form of springs, between which the arm slides. This is for the purpose of getting a clean contact and a sure one, owing to the friction to which the contacts are subjected every time they are brought into operation. Other forms of contacts maybe substituted for the springs; but we prefer the form shown.

Instead of forming a part of the branches which include the motor, magnets G and H may be included in the branches which return directly to the battery, whereby they will get the full strength of the battery-current without the introduction of the resistance of the motor.

The dotted circuits show the old arrangement of circuits upon which our own constituted an improvement.

The invention maybe applied to any other automatic contact-maker as well as to a thermostat-for example, to a steam-gage. In the claims it is intended to cover such similar devices by the word thermostat.

Having now described our invention, what we claim is- 1. In a thermostat, an expansible piece forniing a terminal of an electric circuit, contactpieces forming corresponding terminals, each located in a separate branch circuit, and a pair of electro-magnets one in each branch the two magnets having a common armature, all in combination with a short'circuit terminal on each side of the armature, whereby the contact-points on either side will be automatically short-'circuited, as and for the purpose set forth.

2. In a thermostat, an expansible piece form ing a terminal of an electric circuit, contact pieces forming corresponding terminals, each located in a separate branch circuit, and a pair of electro-m agnets one in each branch the two magnets having a common armature and a moving arm connected therewith, all in combination with a short-circuit terminal on each side of the armature, whereby the con tact-points on either side will be automatically short-circuited, as and for the purpose set forth.

3. The combination, with an electro-magnetic motor and a pair of branch circuits connected therewith, of a thermostat adapted to close one branch or the other on an increase or decrease of the temperature, and an electro-magnetic cut-out for closing a short circuit around the thermostat-contacts, such cutout consisting of a magnet in each branch circuit, the two magnets having a common armature, which co-operates in its reverse positions with the terminals of the short circuit, which are also elements of the combination, as and for the purpose set forth.

In testimony whereof we affiX our signatures in presence of two witnesses.

ETNA HYDE DAVIS. REUBEN IVESTERVELT.

\Vitnesses:

STEPHEN W. TROWBRIDGE, CHAs. HALL ADAMS. 

